This invention relates to a diagnostic system of an LED lamp system in a motor vehicle of a type having a light control module that connects an LED lamp to an operating voltage source and monitors a current consumption of the LED lamp, with the LED lamp having an LED matrix comprising a plurality of interconnected LEDs, a control circuit for controlling and monitoring the LEDs, and a diagnostic circuit that generates an error signal in case of malfunction.
Lighting equipment, in an increasing number of vehicles, is switched via a light control module. German patent document (DE 43 41 058 C1) discloses a light control apparatus for a motor vehicle, but this example shows that such a device can be structured to be very complex. In this example, both a light control module and a lamp module are structured as xe2x80x9csmartxe2x80x9d components, i.e. equipped with a microcomputer, making such a light control apparatus quite expensive. Especially in the field of motor vehicles, however, for reasons of cost, particularly-uncomplicated structured embodiments of light control devices are preferred.
Usually, a light control module has a device for monitoring current that, for example, indicates to a vehicle driver, in a case of controlled filament lamps, whether a filament lamp must be changed. This is problematic when the controlled lamps in motor vehicles are LED-based lamps which, because of their rate of response, reliability, and design possibilities, are increasingly replacing filament lamps. In order to meet light values required by law, it is necessary to control, or drive, several LEDs simultaneously. In a known manner, serial and parallel connections are used. Control occurs via the light control module, which monitors current consumption of the lamp for short circuits and open circuits. This results in the following problem: when using an LED lamp, the light control module cannot recognize a failure of one individual LED (or LED row) by monitoring current consumption because of relevant tolerances and, where applicable, because of double usages of individual LEDs in different light functions. However, within the lamp, such a diagnostic procedure is possible at low cost.
To provide this diagnostic data to the light control module, it is possible to provide a diagnostic output at the LED lamp that is conveyed to the light control module via a diagnostic wire. Such an arrangement, however, proves to be quite costly.
The wiring cost for an additional diagnostic wire for each LED lamp entails additional expenses; which is also the case for components for issuing the diagnostic signals (output driver, perhaps even a microprocessor) within the LED lamp, with these additional expenses accruing even if the diagnostic capability is not even used in a vehicle.
It is therefore an object of this invention to provide a diagnostic system for an LED lamp in a motor vehicle that is particularly uncomplicated and inexpensive in construction.
According to principles of the invention, in case of malfunction, a diagnostic circuit modulates current consumption of an LED lamp via a switchable current sink depending on a type of malfunction that has occurred, and a light control module converts the modulated current into a voltage signal, with the type of malfunction that has occurred being recognized from the voltage signal.
Thus, advantageously, the diagnostic system according to the invention does not require its own diagnostic wire, since the diagnostic information occurs through current modulation on a supply wire of the LED lamp.
Additionally, the cost of components for generating, transmitting, and evaluating the diagnostic information in the LED lamp and in the light control module is exceptionally low. Special inputs and outputs are no longer required for the diagnostic information.
Additional advantageous embodiments and further enhancements of the diagnostic system are possible within this invention.